In diabetes mellitus, vision changes are caused by which process in the retina?

• A. Lack of glucose in retina
• B. Inadequate glucose supply to rods and cones
• C. Neovascularization
• D. Destructive effect of ketones on retinal metabolism

Answer: (C)

Retinal neovascularization caused by ischemia is what leads to vision changes in diabetes. Chronic high blood sugar injures the small vessels of the retina, reducing oxygen delivery (ischemia). In response, the retina releases vascular endothelial growth factor, prompting new, fragile blood vessels to grow on the surface of the retina and optic disc. These vessels are prone to bleed and can form scar tissue that pulls on the retina, potentially leading to vision loss or detachment. This proliferative retinopathy is the main mechanism behind diabetes-related vision changes.

The other ideas don’t fit because the retina isn’t simply lacking glucose; its problem is microvascular damage causing ischemia and compensatory neovascularization. Ketone bodies don’t directly destroy retinal metabolism in this context; the key process is the abnormal growth of vessels driven by hypoxia.